Electronic computer



y 1949- R. L. SNYDER, JR., ETAL 2,471,788 ELECTRONIC COMPUTER Original Filed March 31, 1942 I 3 Sheets-Shut 2 Ii/TRT IZET? R 3nuentom Jan A.Rajc h1mtn (Ittomeg H R iclzard L. Snyder J1:&

y 1949- R. SNYDER, JR., ETAL 2, ,7

ELECTRONIC COMPUTER Original Filed March 31, 1942 I 3 Sheets-Sheet 3 FJ mN V w. 66 IAUHUAUAVAVA A 7 Snnentors Gttorneg Patented May 31', 1949 2,471,788 ICE ELECTRONIC COMPUTER Richard L. Snyder, Jr., and Jan A. Rajchman, Princeton, N. J., assignors to Radio Corporation of America, acorporation of Delaware Original application 'March 31, 1942, Serial No.

437,002, now Patent No. 2,431,591, dated N ovember 25, 1947. Divided and this application February 15, 1947, Serial No. 728,802

This invention relates generally to computers and particularly to electronic computers for substantially continuously deriving a current or an indication which is a predetermined mathematical function of the variable angular displacement of two elements.

Various mechanical computers have been used heretofore, which utilized trains of cams, gears or otherelements for the solution of complex mathematical problems. It is the purpose of this invention to provide ineans'for deriving electric currents which are characteristic of a desired functlonof the angular displacement of two me- 'chanical elements, and utilize the currents to actuate an indicator or operating mechanism associated therewith. This is accomplished by light scanning a surface having fiducial marks of predetermined characteristics and arrangement, masking the surface by means of fixed and movable masks to form an aperture having anopening proportional to the angular displacement to be measured, and'deriving an electric current by means of a light responsive device associated with the unmasked fiducial marks.

One of the objects of the invention is, to provide means for deriving trains of current pulses of a duration which is a function of the variable angular displacement of two elements. Another object is to provide means for scanning an aperture formed by two masking elements, the opening of said aperture being proportional to a function of the angular displacement to be observed, and an electronic device for deriving an indicae tion of the characteristics of the scanned aperture.

' Another object of the invention is to provide mechanical means for forming an aperture which 5 Claims. (Cl. 177-351) is proportional to a function of the unknown angular displacement of two elements, scanning said aperture by a light beam, deriving electrical pulses from fiducial marks scanned through said aperture and providing an indication of the number of the electric pulses so derived.

Still another object of the invention is to provide means for deriving electric pulses of frequency and trains of pulses of duration which are a predetermined function of the angular displacement 'of two elements.

The present application is a division of a, copending application Serial No. 437,002 filed March 31, 1942, now Patent No. 2,431,591.

The invention will be described by reference to the drawings of which Figure 1 is an elevational view, partly in section, of one embodiment; Figure 2 is a perspective view of second embodiment; Figure 3 is a schematic diagram of a third embodiment; Figure 4 is a typical graph of .the electric pulses derived from the light scanning means; Figure 5 is an elevational view of the aperture forming a portion of the scanning 2- means of Figure 3; Figure 6 is a modification of the device shown in Figure 5; Figure 7 is a schematic diagram of the circuit which utilizes the pulses derived from these scanning means; and Figure 8 (tr-g inclusive) is a series of graphs indicating the operating characteristics of the various circuit elements of Figure 8. Similar reference numerals are applied to similar elements throughout the drawings.

Figure 1 illustrates a mechanical arrangement for deriving pulses which are a function of "the scanning of fiducial marks. The motor shaft 52 drives a flywheel "II carrying the light source 59 and the light responsive device 66 which are connectedto slip rings '12 in contact with the brushes 73. A transparent. disc I63 having opaque fiducial marks [64 is disposed between thelight source 56 and the light responsive device 60 so that when the carrier II is rotated, the light beam between the source 59 and the light sensitive device 66 scans the fiducial marks I64. An adjustable mask I which may act in conjunction with a fixed mask attached to the transparent disc I63 is fixed to the bearing supported on the shaft I6 which is supported by the bearlllg I5 mounted on the bracket 74. A handle 68 or other actuatin device is used for the adjustment of the mask I65 to vary the region of the disc I63 scanned during each revolution of the carrier II. The electric pulses derived from the light responsive device 66 are connected through the slip rings 72 and brushes l3 and the switch 6I to either an electronic counter 62 or a frequency measuring circuit hereinafter described in connection with Fig. '7.

Fig. 2 is a perspective view of a similar means for scanning fiducial marks, in which the mirror I55 is driven, for example, in simple harmonic motion. Light from the source 59 is focused on the mirror I55, reflected therefrom to the fiducial marks 64 on the inside surface of the cylindrical support 63, reflected back to the mirror I55 and thence reflected to the light responsive device 66. A fixed mask 66 and a movable mask 65 can be adjusted with respect to each other to limit the aperture through which the fiducial marks will reflect the light beam back to the mirror I 55. It should be understood that the movable mask 65 may be actuated in any desired manner to form an aperture proportional to the angular displacement of the two elements which is to be measured.

Fig.3 is a schematic diagram of a device utilizing a rotating disc 276 having a narrow radial slit 274. A transparentdisc 263 having opaque fiducial marks 264, a fixed mask 266, and a movable mask 265 are disposed adjacent the rotating disc 2') and coaxial therewith. Light from the source 59 is interrupted by rotating slit 214 of disc 210 thereby to scan the flduclal marks 264.

The relative adjustment of the fixed mask 256 and movable mask 265 determines the angle of the fiducial marks scanned by the rotating light beam. The light beam, after passing through the discs, is directed to the spherical reflector l and is reflected therefrom to the light responsive device 60. Electric pulses derived from the light responsive device 60 are utilized in the electronic counter 62 or the circuit of Fig. 7 as indicated above.

Fig. 5 is an elevational view of the arrangement of the scanning disc, transparent disc having fiducial marks, and the fixed and movable masks of the device schematically shown in Fig. 3. In the device of Fig. 5, the fiducial marks are arranged radially to have equal angular displacement.

Fig. 6 is similar to Fig. 5 with the exception that the fiducial marks are straight lines parallel to a diameter of the disc 263. The arrow indicates the direction of the light beam in scanning the fiducial marks. Fiducial marks of the type shown in Fig. 6, will produce light interruptions proportional to the sine of the angular displacement of the fixed and movable masks. The fiducial marks can, of course, be spaced and arranged to provide interruption of the light beam of sequence proportional to any other trigonometric function such as the cosine, tangent, co-

tangent, secant or cosecant. Likewise, the interruption of the light beam can be of sequence proportional to an exponential of the quantity to be measured.

Referring to Fig. '7, the circuit for utilizing the voltage pulses derived from the light responsive device 60 utilizes a unique arrangement of thermionic tube circuits including a bandpass filter, one or more saturation amplifiers, a differentiating circuit, a peak amplifier, and a novel trigger circuit, as well as means for damping the difierentiating circuit and the trigger circuit. These elements are arranged as follows:

The source of voltage pulses, which may include a plurality of frequency components, is applied to the input terminals ill of a filter cir- 4 biased to amplify only the voltage peaks of th applied signal. The cathode circuit of the peak amplifier 5 includes a cathode resistor 22. Voltage across this resistor is applied to the cathode circuit of a first trigger tube 1. The control electrode of the tube 1 is connected to the anode of a second diode 6, to one terminal of the grid resistor l5, and to one terminal of the capacitor l3. The cathode of the second diode 6 and the remaining terminal of the resistor l5 are connected to ground. The remaining terminal of capacitor I3? is connected to the anode of the second trigger tube 8 and to one terminal of a resistance network 23. The remaining input terminal of the resistance network 23 is connected to a source of anode potential for the second trigger tube 8. The anode of the first trigger tube 1 is connected to the control electrode of the second trigger tube 8 and to one terminal of a coupling resistor I4. The remaining terminal of the resistor I4 is connected through the resistor 25 to a source of anode potential for the first trigger tube 1.

The operation of the circuit is as follows: The desired frequency component of the signal to be measured is derived from the filter 9 and applied to the control electrode of the first tube l which provides high amplification and, because "of its saturation characteristics, clips the peaks The signal is further amof the signal wave. plified and clipped by a similar action in the second tube 3 and applied as a signal of substantially square wave form to the input of the third tube 3. When the switch 20 is connected to the inductor I l, the third tube 3 is operated to shockexcite the tuned circuit comprising the natural resonant characteristics of the inductor II, to derive a series of pulses of decreasing amplitude from each square wave pulse applied to the circuit. The first diode 4 provides considerable damping of the pulses of decreasing amplitude to eliminate substantially all of the pulse signal except the first positive cycle. If the switch 20 is connected to the resistor IS, the resistance cuit 9 which is designed to pass the frequency band which is to be measured. The output of the filter 9 is applied to the grid circuit of a first thermionic tube I The grid bias is adjusted to limit the amplitude of the signals to be measured in order to eliminate, as much as possible, response to extraneous signals. The first tube l is operated at the saturation portion of its static characteristic in order to derive an output sig-- nal which is substantially of square wave form. The signal is further amplified by a second thermionic tube 2 which is also operated at the saturation point of its static characteristic in order to further improve the square wave form of the signal. The signal of substantially square wave form is next applied to the-input circuit of a third thermionic tube 3. The anode circuit-of the third tube 3 includes a two-position switch 20 whichis connected in one position to one terminal of a resistor l9 and in another position to one terminal of an inductor H. The movable arm of the switch 20 is connected to the cathode of a first diode 4 and to one terminal of the capacitor 2|. The remaining terminals of the resistor l9, inductor H- and the anode of the diode 4 are all connected through an anode resistor 24 to the source of high potential for the anode of the third tube 3. The remaining terminal of the capacitor 2| is connected to the control electrode of a peak amplifier 5, which is capacity network l9-2I acts as a differentiating circuit. In this network the voltage across the capacitor 2| will be substantially proportional to the rate of change of the square wave signal applied to the network and will therefore include only a sharp positive and negative pulse for each cycle of the square wave signal. When using the diiferentiating network, the damping diode 4 may be omitted, since it will have little effect on the circuit operation.

Signals derived from the circuit with either position of the switch 20 are then applied as pulses to the control electrode of the peak amplifier tube 5. If desired, either the inductor II or the resistor I9, and the switch 20 may be omitted. This tube is biased to clip off and amplify only a positive peak portion of the pulse applied to the control electrode. Sharply peaked voltages from the cathode resistor 22 of the tube 5 are applied to the input circuit of the first=trigger tube 1.

The operation of the trigger circuit is as follows: The first trigger tube 1 is biased so that it is normally conducting while the second trigger tube 8 is biased so that it is normally non-conducting. When a positive pulse from the peak amplifier tube 5 is applied to the cathode of the first trigger tube 1, the first trigger tube 1 is biased to cut-off and the second tube 8 is made to conduct. This condition continues after the exciting pulse has passed, and until the grid of the first trigger tube I, which has been driven to trigger tube '8'will become conducting depends upon the capacitance of the capacitor iii, the grid capacitance of the first trigger tube 1, the

resistance of the resistors l4 and IS, the cutv ofi voltage of the first trigger tube 1 as well as the rate of change of the maximum voltage on the anode of the second trigger tube 8 when the tube is suddenly made toconduct. Since all of these constants can be calculated and fixed, the circuit can be adjusted to any desired time constant.

The limit frequency of the circuit is dependent on the time requiredfor the trigger tubes to return to their normal bias condition after actuation by an exciting pulse. This time interval may be greatly reduced by the use of the second diode 8 which has a dampingiaction on the grid circuit of the first trigger tube 1 by providing substantial attenuation in the circuit when the grid of the first tube I is at positive potential. The action of the diode 8'also tends to make the duration of the current pulse in the anode circuit of the second tube 8 more uniform. The amplitude of this pulse may be maintained at a substantially constant level by proper voltage regulation of the potentials applied to the trigger tube circuits. The current derived from the output terminals ll of the resistance network 23 will be a farily accurate indication of the average rate of occurrence of the exciting pulses applied to the cathode of the first trigger tube 1.

Fig. 8a of the drawing shows a sine wave signal applied to the'input circuit of the first saturation amplifier tube I. Fig. 8b shows a signal of substantially square wave form derived from the anode circuit of the second tube 2 and applied to the input circuit of the tube 8. Fig-8c shows the wave form comprising pulses of diminishing amplitude derived from. the tuned circuit II when the switch 20 is connected to the inductor H. Fig. 8d shows the damping of the pulse current of the first diode 4. The portion of the graph above the dashed line P indicates the positive portion of the pulse current which actuates the peak amplifier 5. Fig; 8e shows the positive pulse derived from across the resistor 22 in the cathode circuit of the peak amplifier I. Fig. 89 shows the potential variations on the gridof the first trigger tube 1 caused by the application of the pulse shown in Fig. 8e. Fig. 8! shows the corresponding potential variations in the anode Y circuit of the second trigger tube 8 which are applied to the resistance network 23. The dashed lines in Fig. 8g indicate the damping action of the second diode 8 and clearfy show the action of this tube in decreasing the time required for the trigger-tubes I and Ito return to their nor- 7 mal bias condition.

we claim as our invention: a 1. In a computer for substantially continuously deriving a mathematical function of the variable angular displacement of two elements, a disk 7 reflector and from said reflector to said device to derive trains of electrical pulses the duration of each said train being a function of said unmasked marks.

2. In a computer for substantially continuously deriving a mathematical function of the variable angular displacement of two elements, a support having a semicircular area having fiducial marks all of which are parallel to its diametrical edge, means for selectively masking a predetermined portion of said area, and means associated with said marks for deriving trains of current pulses, the number of pulses of said train being a trigonometric function of the ratio of said unmasked to said masked surfaces.

3. The combination of a support bearing fiducial marks on one of its surfaces, means forming a beam of light, fixed and movable masks interposed in the path of said beam for variably exposing said surface, means. for moving said beam to scan said surface, and means responsive to light transmitted through the exposed area of said surface for deriving current pulsetrains of a duration which is a function of the ratio of the unexposed to the exposed area of said surface.

' 4. The combination of a support bearing fiducial marks on one of its surfaces, means forming a beam of light, fixed and movable masks interposed in the path of said beam for variably exposing said surface, means including a rotatable disk provided with a narrow slit for moving said beam to scan said surface, and means responsive to light variations produced by the exposed area of said surface forv deriving current pulse trains of a duration which is a function of the ratio of the unexposed to the exposed area of said surface.

5. The combination of means providing a transparent area bearing fiducial marks, means forming a beam of light, means for variably masking said transparent area, means for moving said It should be understood that the filter 9, tubes l, 2, l, 4 and 8, or any of them, may be. omitted if the signal'to be measured has suitable characteristics for the actuation of the trigger circuit comprising the tubes 8, 1, and 8. It should also be understood that the second diode 6 may be omitted if the operating frequency of the circuit is sufficiently low to permit the trigger tubes 1 and 8 to return to normal bias condition without the damping action of the diode I.

,beam to scan said transparent area, and means responsive to light transmitted through the unmasked part of, said area during said scanning for deriving current pulse trains of a duration which'is a function of the ratio of the unexposed to the exposed part of said area.

RICHARD L. SNYDER, Jn. JAN A. assent/IAN.

REFERENCES orrEn The following references are of record in th file'of this patent:

UNITED STATES PATENTS 

